This is a multi-disciplinary integrative proposal that utilizes Functional Genomic tools, phytoplankton ecology and satellite imagery to better understand the distribution and molecular mechanisms affecting harmful algae blooms (HAB) in sub/tropical marine ecosysytems. This research is proposed to provide better predictive ability about HAB affect on human health. Phytoplankton that make up HAB regulate gene expression by altering mRNA levels (Pichard1993; Pichard et al., 1997; Wyman et al., 1998; Amaro et al., 2000; Paul et al., '00; Taroncher-Oldenburg 2000). This proposal seeks to create 10,000s of the dinoflagellate Karenia brevis EST[1] to manufacture microarrays. These microarrays will be used to quantify patterns of mRNA expression, and thus lead to the discovery of genes that reflect changes in population growth, environmental change or toxin production. Microarrays of K. brevis genes will be used to achieve four overall goals to: (1) quantify variation in mRNA expression among populations in bloom and non-bloom conditions; (2) quantify patterns of gene expression among cultures of K. brevis exposed to different environmental conditions; (3) use genetic markers to discern population divergence among blooms, and (4) examine variation in gene expression among different populations. To interpret these data, microarray studies will be combined with analyses of toxin production, ecological and physiological measures and satellite imagery. These diverse approaches will allow the investigators to interrogate patterns of gene expression and thus discover genes involved in HABs. These studies will provide linkages between population genetics, biological oceanography, and functional genomics to better inform scientific and public concerns about the ocean's affect on human health.